Rotation angle detection apparatus and rotary disk for same

Abstract

A rotation information record surface of a rotary disk is disposed at an intermediate position between a fixing point of the rotary disk and a rotary shaft and a fixing position of a detection head, so that a stable gap can be obtained with a variation due to thermal expansion being reduced. In order to attain this, the fitting portion of the rotary disk is shaped to have a first fitting portion and a second fitting portion. The first fitting portion is provided for attaining satisfactory coaxiality, and the second fitting portion is adapted to form a clearance into which bonding means such as an adhesive is to be infused. With the above structure, an optimum detection position (i.e. an optimum gap position) would not be varied by a change in the ambient temperature.

1. A rotation angle detection apparatus comprising:
 a rotary shaft; 
 a rotary disk that is made of a synthetic resin material, fixed to said rotary shaft and having a rotation angle information record part; and 
 a sensor portion that detects information from said rotation angle information record part; 
 wherein said rotary disk is attached to said rotary shaft in such a way that a direction of shift of said rotation angle information record part of said rotary disk in the thrust direction caused by variation in temperature and a direction of shift of said rotary shaft in the thrust direction caused by variation in temperature would cancel each other. 
 
   
   
     2. A rotation angle detection apparatus according to  claim 1 , wherein said rotary disk is provided with:
 a fixing portion to be fixed to said rotary shaft; 
 a cylindrical portion extending from an outer peripheral portion of the fixing portion in a direction along an axis of said rotary shaft; and a disk body portion extending from an end portion of the cylindrical portion in a direction perpendicular to the axis of said rotary shaft; 
 wherein said rotation angle information record part is disposed on said disk body portion.